Digital Visual Interface and High-Definition Multimedia Interface are high speed serial interconnect standards to transmit graphical data from a source to some type of display. The standards operate over a large range of data rates at very low differential voltage levels. The interface connection is limited to relatively short distance due to the combination of high data rates (250 Mb/s to 1.65 Gb/s), low voltage swings (800 mV), reflections with the signal due to cable and connectors, and compatibility issues between manufactures of the transmitters and receivers.
One solution to the limitation of a relatively short distance is to transmit the Digital Visual Interface and/or High-Definition Multimedia Interface data over an optical fiber to increase the distance between the source and display. This solution is realized by converting each electrical bit into an optical on/off state using a laser. The receiver at the other end of the fiber will use an optical detector and electronics to convert the optical state into an electrical state.
However, this solution requires that each electrical channel be mapped 1:1 to an optical fiber channel. In current graphic and video applications using Digital Visual Interface and/or High-Definition Multimedia Interface, three channels are utilized for graphic data, a single channel for the clock, a single channel for upstream control data, and a single-channel for down stream control data.
FIG. 1 illustrates an example of this conventional system. In FIG. 1, a digital video source 20 is optically connected to a display device 30 through an optical cable 10. This system requires numerous lasers, detectors, and fibers to establish a link between the source 20 and display 30.
As illustrated in FIG. 2, the system of FIG. 1 requires numerous fibers that add cost to the system. In FIG. 2, the optical cable 100 includes three fiber (A, B, C) for graphic data, a single fiber (D) for the clock, a single fiber (E) for upstream control data, and a single fiber (F) for down stream control data. It is noted that a fewer number of fibers can be used, but in such configurations, the control data and return data are omitted from the system, thereby not complying with the specification of Digital Visual Interface and/or High-Definition Multimedia Interface.
As noted above, optical fibers can be employed to transmit high volume of information fast and reliably. The optical fibers include silica optical fibers, such as silica single-mode optical fibers, plastic optical fibers, and other fibers. In particular, the plastic optical fibers have a larger diameter than the silica single-mode optical fibers and are excellent in flexibility. From this viewpoint, the optical cables, which employ plastic optical fibers has optical transmission lines, are excellent in workability in end treatment and connection treatment of the optical fibers needed during installation, and in wiring. The optical cables are effective as a short distance trunk in a building after lead-in from a trunk cable, a branch cable, or a line cable for a LAN system.
The optical cables are usually configured to cover optical fibers and tensile strength reinforcing members (tension members) for avoiding elongation of the optical fibers due to tension with a sheath. In general, the optical fibers have a primary resin covering applied on a surface to prevent disturbance light from entering, to avoid damage due to a mechanical external force, or for another reason. In the case of optical cables for communication, two or more optical fibers for both input and output are usually housed.
As noted above, some optical cables use added tension members within the sheath of the optical fiber assembly to provide greater tensile stiffness than the fiber used in the assembly. This is needed to help reduce cable stress that will in time add additional loss in the fiber. Adding the extra tension member to the fiber assembly is commonly used with plastic optical fiber, but can be used with any fiber type that can benefit from the added tensile strength.
With respect to another example of a conventional Digital Visual Interface and/or High-Definition Multimedia Interface system, the data transfer system sends data back and forth from point A to point B; however, the data transfer system does not send the same amount of data in one direction as in the other direction. More specifically, in the conventional system, Point A could be sending data at 2 Gb/s to point B, but Point B is only sending 1 Mb/s of data to Point A. Typically, this type of system would require two fiber channels, one for the high speed downstream data and one for low speed upstream data, or a single mode system that creates bi-directional data stream with two different wavelengths, which adds additional circuitry.
Moreover, graphic applications operate at different clock rates for different display resolutions. However in many data transfer architectures it is beneficial to transmit the data at a fixed data rate. The problem in realizing this benefit is providing an adequate conversion of the variable rate data being received by the converter to a fixed data rate for actual transmission, and then a conversion of the fixed rate data back to a variable rate data without loss.
Lastly, Digital Visual Interface and/or High-Definition Multimedia Interface systems send graphic data and control data from the source to the display, as well as, sending control data from the display to the source. The graphic data, conventionally, is transmitted at a high data rate, while the control information is transmitted at a lower data rate. Since control data is flowing in both directions, the conventional systems have utilized bi-directional links. However, utilization of bi-directional links adds an extra channel to the communication cable, thereby increasing its costs.
Therefore, it is desirable to provide a Digital Visual Interface and/or High-Definition Multimedia Interface system that provides a fixed rate of data transmission between a source and a display with a proper conversion from a variable data rate to a fixed data rate and back to a variable data rate without loss of data.
Moreover, it is desirable to provide a Digital Visual Interface and/or High-Definition Multimedia Interface system that utilizes a communication cable that provides bi-directional communication of the control data without increasing the cable's cost.
Also, it is desirable to provide a Digital Visual Interface and/or High-Definition Multimedia Interface system that utilizes bi-directional communication of the control data without increasing the cost of the system.
It is further desirable to provide a Digital Visual Interface and/or High-Definition Multimedia Interface system that utilizes a protocol which enables the reduction of channels needed in a communication cable.